Along with Robert Jay Charlson, James Lovelock, and Stephen G. Warren, he developed the CLAW hypothesis, named after the initials of the authors.
This hypothesis states that dimethyl sulfide from the ocean is converted in the atmosphere to sulfate particles, which then influence the formation of clouds and therefore the climate.
Other works from this period were concerned with biogeochemical transformations of compounds of arsenic, antimony, selenium, tellurium and tin in the marine and terrestrial ecosystems.
On expeditions in the Congo, the Amazon, and Southern Africa he studied the emissions from vegetation fires, the exchange of trace gases, and the production of biogenic aerosol particles.
In 2009, he set up a new working group, applying methods of isotope geochemistry and mass spectrometry to problems of paleoclimatology and marine biogeochemistry.